MVHR installers or alternatives?

[Eastfield]

12 hours ago, G and J said:

I’m not sure I agree that it’s impossible to calculate a payback for the cost of MVHR because using Jeremy’s spreadsheet our heating requirement is a lot less than half of what it would be with sub one air changes per hour compared to say five air changes per hour that you’d need with a non-heat recovery system.

 

However, the extra spend to get airtight would be quite difficult to calculate and indeed we’ve not done a cost benefit calculation in payback terms, we’ve gone for it just as an act of faith for comfort.  So despite it being theoretically possible, I think calculating payback for MVHR for us at least is rather pointless. 

Excuse my ignorance, but why do you need such a higher number of changes per hour with a non-heat recovery system?

[G and J]

I think you need a certain number of air changes per hour to keep all fresh.  
 

With trickle vents it’s a blow through.  But with MVHR one still (as I understand it) get a good flow through if fresh air.  
 

It at first appears confusing that we have a really low air change score to make MVHR worth having, but that’s a test if the leakiness of the house, not the number of air changes that a good ventilation system will give.